In network communication and when a network state is good, a network may not truncate a data stream (for example, a voice signal stream) sent by a sending end but directly send it to a receiving end, and the receiving end may obtain a whole-band signal through decoding according to the data stream sent by the network and output the signal to a user for listening. When the network state is poor, the network may truncate the data stream sent by the sending end in different lengths, and the receiving end may obtain a lower-band signal or a whole-band signal through decoding according to the truncated data stream sent by the network and output the signal to the user for listening. Switching between the lower-band signal and the whole-band signal exists at signal outputting at the receiving end, and such switching between signals of different bandwidths usually leads to bad audio influence on the user, and reduces user experience. Therefore, for the receiving end, the lower-band signal after decoding needs to be further expanded into the whole-band signal, so as to reduce an abrupt change of the bandwidth, reduce the audio influence on the user, and improve the user experience.
In the prior art, when a lower-band signal is expanded into a whole-band signal, usually a default bandwidth is used as an estimated bandwidth corresponding to the whole-band signal that the lower-band signal is expanded into, which brings audio influence on the user when the lower-band signal is expanded into the whole-band signal, and reduces the user experience.